Carburetors of the kind described above are known from published German patent application No. DE-OS 3,127,516. In this known carburetor, the inlet valve is opened by means of the pressure of the fuel pump which occurs when starting the engine so that the fuel can flow into the control chamber and through the inlet channels into the intake pipe. As soon as the engine is started and runs, a switchover valve interrupts the applied pressure so that the inlet valve returns to its closed position. Especially with longer use of the carburetor, the danger is presented that the inlet valve becomes dirtied by the combustion residue in the crankcase so that it can no longer close without difficulty. Disturbances during normal operation of the carburetor can occur in this way.